The present invention relates to a fabric with an optimized weave of the multiple-linked ply type that is suitable for use in producing composite material parts that are highly stressed in tension, compression, or bending, and/or that are subjected to impacts. Such parts include, for example, the stays, rods, and struts of landing gear.
Textile structures are known that are referred to as 1D or 2D structures, depending on whether their fibers extend in one direction only or in two different directions. In general, such structures do not make it possible to withstand the above-mentioned stresses effectively. So-called 3D structures that comprise fibers extending in three distinct directions in three-dimensional space are better at withstanding said stresses. So-called 4D, 5D, 9D, 11D, . . . structures are known to exist that comprise fibers extending in a larger number of distinct directions, but those structures are very complex and it is difficult to automate production thereof.
The invention thus relates more particularly to 3D textile structures.
These structures include 3D structures having a plurality of layers linked together by stitching. These structures are known to present good linearity when the weft fibers are bent, and they offer the advantage of including reinforcement. However, that method of linking does not impart good impact resistance to a part produced from such a fabric.
Multi-ply fabrics that are linked together by weaving are also known, with the orthogonal type 3D fabric (in which the ply-linking fibers extend substantially orthogonally to the plies) being the fabric that presents the best linearity for the weft fibers and the warp fibers (i.e. paths with small linking angles or small amounts of curvature), thereby withstanding compression well. Nevertheless, in order to ensure that such fabrics present an advantageous fiber volume fraction, it needs to be compressed, such that the yarns that are orthogonal to the plies and that serve to connect them to one another acquire large amounts of curvature, giving them highly undulating paths that are thus not very linear, which means that they cannot contribute effectively to transferring forces.
Although non-orthogonal 3D fabrics are more advantageous in this respect, they nevertheless suffer from the drawback of presenting linking fibers having linking angles or amounts of curvature that are too great, regardless of whether the weave of the fabric is simple, of the multi-ply taffeta, satin, or serge type, or the weave is more elaborate, such as the 3X type weave.
The fabric known as “2.5D” fabric, described in document FR 2610951, is particularly optimized and presents little expansion and a high percentage of surface occupation, but at the price of poor linearity (i.e. at least some of the fibers present large amounts of curvature or large linking angles). The definition of that fabric gives it angle characteristics that are harmful to withstanding impacts and limits reversible textile structures (i.e. structures obtained by turning the weave through 90°) to structures of low density, unless large numbers of additional plies are added, which makes automatic fabrication difficult.
The fabric described in document U.S. Pat. No. 5,899,241 is particularly optimized for withstanding impacts. Nevertheless, the high degree of interlacing between the plies limits the compression strength of an element made from such a fabric.